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For some birds, recognising their own eggs can be a matter of life or death.

Scientists have used imafe recognition technology to show that birds defending their nests against the Common Cuckoo - which lays its lethal offspring in other birds' nests - have evolved distinctive patterns on their eggs in order to distinguish them from those laid by a cuckoo cheat.

These patterns provide a defence against the cuckoo's trickery by helping birds reject the cuckoo eggs before they hatch and destroy the host's own brood.

Scientists have shown that birds defending their nests against the Common Cuckoo - which lays its lethal offspring in other birds' nests - have evolved distinctive patterns on their eggs in order to distinguish them from those laid by a cuckoo cheat. A tool is used to extract visual features (shown in magenta) on the eggs

Scientists from the University of Cambridge and Harvard University, in Cambridge, Massachusetts, have developed a new computer vision tool to unravel how a host bird may perceive and recognise such complex pattern information.

The Naturepatternmatch tool extracts and compares recognisable features, recreating processes known to be important for recognition tasks in birds

'We harnessed the same computer technology used for diverse pattern recognition tasks, like face recognition and image stitching, to determine what visual features on a bird's eggs might be easily recognised,' said Dr Mary Caswell Stoddard at Harvard University.

Using the tool, the researchers studied the pigmentation patterns on hundreds of eggs laid by eight different 'host' bird species targeted by the Common Cuckoo.

They discovered that some hosts, like the Brambling, have evolved highly recognisable egg patterns characterised by distinctive blotches and markings. However, other hosts have failed to evolve recognisable egg patterns and instead lay eggs with few identifiable markings.

Egg patterns help birds reject cuckoo eggs before they hatch and destroy the host's own brood. Here, a duped Reed Warbler cares for a cuckoo chick

The scientists found that the hosts with the best egg pattern signatures are those that have been subjected to the most intense cuckoo mimicry.

The Common Cuckoo and its hosts are locked in different stages of a co-evolutionary arms race.

If a particular host species over time develops the ability to reject foreign cuckoo eggs, the cuckoo improves its ability to lay eggs that more closely match the colour and patterning of those laid by its host.

Dr Stoddard said: 'The ability of Common Cuckoos to mimic the appearance of many of their hosts' eggs has been known for centuries.

'The astonishing finding here is that hosts can fight back against cuckoo mimicry by evolving highly recognisable patterns on their own eggs, just like a bank might insert watermarks on its currency to deter counterfeiters.'

Professor Rebecca Kilner, of the University of Cambridge, said: 'The surprising discovery of this study is that hosts achieve egg recognition in different ways.'

Some host species have evolved egg patterns that are highly repeatable within a single clutch.

Other species have evolved eggs with patterns that differ dramatically from female to female in a population, according to the study which was published in the journal Nature Communications.

While other host species produce egg patterns with high visual complexity, each strategy is effective, increasing the likelihood that a given host will identify and reject a foreign egg.

Professor Kilner said: 'Some species use two of these strategies, but none uses all three. A signature like this would be too complex to be easily recognised.'